1. Field of the Invention
Embodiments of the present invention generally relate to refractory metal silicon nitride layers and, more particularly, to methods of forming titanium tantalum silicon nitride (TixTay(Si)Nz) layers.
2. Description of the Related Art
Integrated circuits (ICs) typically include metal conductive layers that are used to interconnect various individual devices of the IC. As the density of integrated circuits increases, more and more levels of metallization are employed to provide electrical connections to these devices.
The metal conductive layers are typically isolated from each other by one or more dielectric material layers. Holes (vias) formed through the dielectric layers provide electrical access between successive conductive interconnection layers.
For the current subhalf-micron (0.5 μm) generation of semiconductor devices, any microscopic reaction at an interface between interconnection layers can cause degradation of the resulting integrated circuits (e.g., increase the resisitivity of the interconnection layers). Barrier layers prevent degradation at interfaces between conductive and dielectric layers and have consequently become a critical component for improving reliability of interconnect metallization schemes.
Refractory metal silicon nitride layers such as, for example, titanium tantalum silicon nitride (TixTay(Si)Nz) layers, have been suggested as diffusion barriers for copper and other interconnect metals. Titanium tantalum silicon nitride (TixTay(Si)Nz) material layers have low resistivities (resisitivities less than about 10 Ω-cm), and show excellent performance in preventing the diffusion of copper into underlying layers as well as preventing the diffusion of fluorine and/or oxygen from low dielectric constant material layers (dielectric constants less than 4) into the copper.
Titanium tantalum silicon nitride (TixTay(Si)Nz) layers may be formed, for example, using two or more chemical vapor deposition (CVD) processes. For example, titanium tetrachloride (TiCl4) and ammonia (NH3) may be thermally reacted to form a titanium nitride (TiN) layer, into which silicon (Si) is subsequently incorporated by plasma annealing the TiN layer using a silicon-containing gas (e.g., silane (SiH4)). Thereafter, the refractory metal silicon nitride layer may be formed by thermally reacting tantalum pentachloride (TaCl5) with ammonia (NH3) to deposit a tantalum nitride (TaN) layer on the titanium silicon nitride (TiNSi) and than annealing the structure to form the titanium tantalum silicon nitride (TixTay(Si)Nz). However, it is difficult to control the amount of tantalum incorporated into the titanium silicon nitride (TiSiN) layer using an annealing process, adversely affecting the barrier properties thereof.
Thus, a need exists in the art for a method of forming titanium tantalum silicon nitride (TixTay(Si)Nz) layers.